Changes in biomass and
chemical composition during lecithotrophic larval development of the
southern king crab, Lithodes santolla (Molina)
G.A. Lovrich, S. Thatje, J. A. Calcagno, K. Anger, A.
Kaffenberger-2003
Journal of Experimental Marine Biology, 288(1): 65-79
Abstract:
Changes in biomass and elemental composition (dry
mass, W; carbon, C; nitrogen, N; hydrogen, H) were studied in the
laboratory during complete larval and early juvenile development of the
southern king crab, Lithodes santolla (Molina), formerly known as Lithodes
antarcticus (Jacquinot). At 6±0.5 °C, total larval development from
hatching to metamorphosis lasted about 10 weeks, comprising three demersal
zoeal stages and a benthic megalopa, with mean stage durations of 4, 7, 11
and 47 days, respectively. No differences in development duration or
mortality were observed in larvae either fed with Artemia sp. nauplii
or unfed, indicating that all larval stages of L. santolla are
lecithotrophic. First feeding and growth were consistently observed
immediately after metamorphosis to the first juvenile crab stage. Regardless
of the presence or absence of food, W, C, N and H decreased
throughout larval development. Also the C:N mass ratio decreased
significantly, from 7.7 at hatching to 4.1 at metamorphosis, indicating that
a large initial lipid store remaining from the egg yolk was gradually
utilized as an internal energy source, while proteins played a minor role as
a metabolic substrate. In total, 56–58% of the initial quantities of C and
H present at hatching, and 20% of N were lost during nonfeeding larval
development to metamorphosis. Nine to ten percent of the initially present
C, N and H were lost with larval exuviae, half of these losses occurring in
the three zoeal stages combined and another half in the megalopa stage
alone. Metabolic biomass degradation accounted for losses of about 47–50%
in C and H but for only 10% in N. Hence, most of the losses in C and H
reflected metabolic energy consumption (primarily lipid degradation), while
about half of the losses in N and two thirds of those in W were due
to larval exuviation. Complete independence from food throughout larval
development is based on an enhanced maternal energy investment per offspring
and on energy-saving mechanisms such as low larval locomotory activity and
low exuvial losses. These traits are interpreted as bioenergetic adaptations
to food-limited conditions in Subantarctic regions, where a pronounced
seasonality of day length limits the period of primary production, while low
temperatures enforce a long duration of pelagic development.